Natural deep eutectic solvent of choline chloride with oxalic or ascorbic acids as efficient starch-based film plasticizers

Abstract

Natural deep eutectic solvents (NADES) of choline chloride/oxalic acid (OA) and choline chloride/ascorbic acid (AA) were evaluated as innovative candidates for cassava starch-based film plasticizers, aiming to replace the glycerol standard. NADES-OA and NADES-AA were compared at five levels with a 40% glycerol standard. NADES were characterized by Fourier Transform Infrared (FTIR), and the films were subjected to optical, physical, and mechanical evaluations and structural analysis by X-ray Diffractometry (XRD) and FTIR. NADES-OA and NADES-AA improved the films' optical, physical, and mechanical properties, providing characteristics similar or superior to those plasticized with glycerol. NADES-OA showed a greater plasticizing effect, requiring a lower plasticizer concentration (30%) for the films to reach similar mechanical and physical characteristics to those with 40% glycerol. In addition, it presented a lower opacity and crystallinity index. Films with 60% NADES-AA had the highest elasticity and the lowest opacity but were highly water soluble and slightly yellow. Novel data reported here indicate that NADES-OA and NADES-AA can be used as efficient plasticizers for starch-based films, presenting vast potential for use as films or coatings for the agricultural and food industries.